When liquid (mordant) is conventionally prepared for a degree of density, manually, a container unit (a measuring cup) is used and put on a balance and then the amount of powder and liquid is calculated upon a required ratio; next, the required amount of powder is put in the container unit, and after the powder reaches a required precise weight, a dropper is used to absorb a required amount of liquid and to drop it in the container unit of powder, and the powder and the required liquid is stirred to mix; if the preparation has not yet completed for the required ratio, the container unit is put on the balance again and then a required amount of powder is put in the container unit; next, after the powder reaches the required precise weight, the dropper is used to absorb the required amount of liquid and to drop it in the container unit of powder, and the powder and the required liquid is stirred to mix; the step is repeated until the liquid prepared reaches the required degree of density.
Although all users follow the method mentioned above to prepare liquid for a density currently, they estimate the value on the balance by the naked eye when adding powder in the container unit; further, the dropper is used manually to absorb liquid and then to drop it in the container unit, so errors occur easily during the preparation so that the density of prepared liquid cannot meet the requirements of use; besides, careful adding and dropping of the required ration of powder and liquid by means of manual work is a must for a precise ratio; therefore, it takes much more time to put powder and drop liquid and keep it under control, which makes the speed of preparation low and thus man hour and working procedure waste.